Balance Sheet Information - Summary of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Payables And Accruals [Abstract]
Inventory receipts	$ 1,894	$ 1,730
Paid time off	1,096	1,011
Payroll, bonuses, and other employee benefits	866	2,780
Warranties	378	382
Deferred revenues	203	189
Real estate taxes	185	148
Customer refunds for estimated returns	184	197
Income and sales taxes	179	243
Professional fees and contractors	163	155
Employee stock purchase plan	140	314
Short-term obligations under capital leases	98	97
Other	401	235
Total	$ 5,787	$ 7,481